Bogota, Colombia (CNN) -- Rescue operations were halted Thursday at a coal mine in northwest Colombia where an explosion killed at least 11 miners and trapped 62 others, a state governor said.

Six of the 79 miners on the shift survived the massive blast and walked out alive, said Antioquia Gov. Luis Alfredo Ramos Botero.

President Alvaro Uribe said on the presidential website that 16 bodies had been recovered. There was no immediate explanation for the discrepancy. Various government agencies and news outlets reported different casualty figures throughout the day.

Search operations were suspended due to the presence of toxic gases and the danger of new explosions, Ramos told CNN en Espaņol. The governor said Thursday afternoon he did not know when the search could continue.

Officials also are concerned about possible cave-ins, said Nicolas Correa, the Antioquia state minister of mines.

The outlook for the miners trapped inside was not good, said state government spokesman Juan Fernando Ortiz..

"Because of the explosion, it is considered very improbable" that they survived, Ortiz told CNN in a telephone interview.

The wife of one of the missing miners said her husband did not want to go to work Wednesday.

"There's no hope of finding them alive," Dora Sanchez said on CNN affiliate Caracol TV.

A survivor described the blast, which officials said was caused by an accumulation of gas.

The blast was so strong that it was felt in the nearby town of Amaga, said resident Virgilina Londono.

Addressing the nation, Uribe called the catastrophe "very sad news."

"This is very grave," Uribe said. "And I give this news to Colombians with much pain."

The explosion at the San Fernando mine occurred Wednesday around 10:30 p.m. local time (11:30 p.m. ET), during a shift change, which meant there were more employees in the mine at the time, said Catalina Rico, a spokeswoman for the Antioquia Disaster Prevention and Attention System.

Rescue and recovery operations could take three or four days, government spokesman Ortiz said.